JP7724980B2 - Electric motor, air conditioner, and control board - Google Patents

Description

This disclosure relates to an electric motor equipped with an inverter, an air conditioner, and a control board.

In recent years, there has been a demand for higher output fan motors (electric motors for fans) in air conditioners to save energy or improve heating capacity. There is also a demand for smaller fan motors to ensure airflow. When fan motors are made smaller while also increasing their output, the temperature of the control board containing the inverter tends to rise. For this reason, there is a need to suppress the temperature rise of the control board containing the inverter.

The electric motor described in Patent Document 1 is integrated with a control board equipped with an inverter. In this electric motor, some of the multiple power relays and multiple switching elements are mounted on different sides of the control board to improve heat dissipation.

Japanese Patent Application Laid-Open No. 2020-195236

However, in the technology of Patent Document 1, components are placed on the control board without considering their operation, which creates the problem that if components with a large amount of temperature rise are concentrated on one side of the control board, the amount of temperature rise suppressed by the control board is reduced.

This disclosure has been made in consideration of the above and aims to obtain an electric motor that can significantly suppress temperature increases in the control board.

To solve the above-mentioned problems and achieve the objectives, the electric motor disclosed herein comprises a stator, a rotor, and a control board having an inverter circuit that supplies current to the stator. The inverter circuit has multiple power transistors in an upper arm and multiple power transistors in a lower arm. The power transistors of the upper arm or lower arm that switches more frequently are distributed across a first surface of the control board and a second surface opposite the first surface.

The electric motor disclosed herein has the effect of significantly suppressing temperature increases in the control board.

FIG. 1 is a diagram illustrating a configuration example of an electric motor according to a first embodiment; FIG. 1 is a diagram showing a circuit configuration of a built-in board included in an electric motor according to a first embodiment; FIG. 1 is a diagram for explaining an example of switching performed by an electric motor according to a first embodiment; FIG. 1 is a diagram showing the arrangement positions of power transistors arranged on a built-in substrate of an electric motor according to a first embodiment; FIG. 1 is a cross-sectional view schematically illustrating a first example of an internal configuration of an electric motor according to a first embodiment; FIG. 10 is a cross-sectional view schematically illustrating a second example of the internal configuration of the electric motor according to the first embodiment; FIG. 1 is a diagram schematically illustrating a first example of an arrangement of power transistors on a built-in substrate according to a first embodiment; FIG. 10 is a diagram schematically illustrating a second example of an arrangement of power transistors on a built-in substrate according to the first embodiment; FIG. 10 is a cross-sectional view schematically showing the internal configuration of an electric motor according to a comparative example. Schematic diagram of an air conditioner according to a second embodiment

Below, the electric motor, air conditioner, and control board relating to the embodiments of the present disclosure are described in detail based on the drawings.

Embodiment 1.
1 is a diagram showing an example of the configuration of an electric motor according to embodiment 1. In embodiment 1, a case will be described in which electric motor 1 is a three-phase electric motor, but electric motor 1 according to embodiment 1 is not limited to a three-phase electric motor.

The electric motor 1 is a brushless DC (Direct Current) motor. In Figure 1, a portion of the electric motor 1 is shown in cross section to explain its configuration. Note that while Figure 1 shows a radial gap type brushless DC motor, the electric motor 1 of embodiment 1 is not limited to a radial gap type brushless DC motor.

The electric motor 1 comprises a rotor 30, a stator 20, an internal circuit board 11 which serves as a control board, and molded resin 12. A rotating shaft 31 is inserted into the rotor 30. The stator 20 is provided on the outer periphery of the rotor 30. The internal circuit board 11 has a circuit board which controls the drive of the rotor 30.

The stator 20, built-in substrate 11, and molded resin 12 are fixed together by the molded stator 10. The molded stator 10 is formed by integrally molding the stator 20 and built-in substrate 11 (insert molding them together). That is, the stator 20 and built-in substrate 11 are fixed together by the molded stator 10. The molded stator 10 also has a recess formed inside it that can accommodate the rotor 30. The stator 20 and built-in substrate 11 may also be molded separately. In this case, the integrally molded stator 20 and the integrally molded built-in substrate 11 are joined together.

The stator 20 has multiple stator cores 21, insulators 23 integrally molded with the stator cores 21, and a winding group 22. The stator cores 21 are constructed by laminating electromagnetic steel sheets. The insulators 23 insulate the stator cores 21 from the winding group 22.

In the electric motor 1, the stator 20 is formed by winding the windings of the winding group 22 around each slot of the stator core 21, which is integrally molded with the insulator 23. Each winding of the winding group 22 is made of copper, aluminum, or the like.

An output side bearing 33 that rotatably supports the rotating shaft 31 is provided at one end of the rotating shaft 31. A non-output side bearing 34 that rotatably supports the rotating shaft 31 is provided at the other end of the rotating shaft 31.

The non-output side bearing 34 is covered by a conductive bracket 60. The bracket 60 has a press-fit portion 61 fitted into the inner periphery of the molded stator 10 so as to cover the opening of a recess provided in the molded stator 10. The outer ring of the non-output side bearing 34 is fitted inside the bracket 60.

The built-in board 11 has a circuit including a control unit 70 (described later) and a magnetic sensor 50 that detects the position of the rotor 30.

The built-in board 11 is disposed perpendicular to the axial direction of the rotating shaft 31 between the output bearing 33 and the stator 20, and is fixed to the insulator 23. The built-in board 11 is provided with a lead outlet 14 from which lead wires 13 are drawn to connect to a higher-level system (for example, a board on the air conditioner unit side). The higher-level system is a system that mounts the electric motor 1. The lead wires 13 are connected, for example, to a board on the air conditioner unit side (such as the indoor unit board 211 described below). Passive components such as operational amplifiers, comparators, regulators, diodes, resistors, capacitors, inductors, and fuses are also disposed on the built-in board 11.

The built-in substrate 11 is, for example, circular in shape with a through-hole formed in the center. However, the built-in substrate 11 may also be shaped other than circular, such as semicircular. The rotating shaft 31 passes through the through-hole provided in the built-in substrate 11. The built-in substrate 11 is arranged inside the electric motor 1 so that the top and bottom surfaces are perpendicular to the axial direction of the rotating shaft 31.

A rotor insulator 32, which is an annular member, is arranged on the outer periphery of the rotating shaft 31. The rotor 30 has a magnet 40 arranged inside the molded stator 10. The magnet 40 is arranged on the outer periphery of the rotating shaft 31, facing the stator core 21. The magnet 40 is composed of a cylindrical permanent magnet. The magnet 40 is fixed to the rotating shaft 31.

Magnet 40 is produced by injection molding a bonded magnet consisting of a ferrite magnet or a rare earth magnet (samarium iron nitrogen, neodymium, etc.) mixed with a thermoplastic resin material. The magnet is incorporated into the mold used to injection mold magnet 40, and magnet 40 is molded while applying orientation. Magnet 40 may also be a sintered magnet.

The magnet 40 has, in the axial direction of the rotating shaft 31, a sensor magnet portion which is the portion close to the magnetic sensor 50, and a main magnet portion which is the portion other than the sensor magnet portion. The sensor magnet portion allows the magnetic sensor 50 to detect the position of the rotor 30. The main magnet portion generates a rotational force in the rotor 30 in accordance with the magnetic flux generated by the winding group 22.

The outer diameter of the magnet 40 on the magnetic sensor 50 side of the built-in substrate 11 is smaller than the outer diameter of the other portions. That is, the outer diameter of the sensor magnet portion of the magnet 40 is smaller than the outer diameter of the main magnet portion. This shape of the magnet 40 makes it easier for magnetic flux to flow into the magnetic sensor 50 mounted on the built-in substrate 11. The magnetic sensor 50 is positioned far from the winding group 22, i.e., close to the rotating shaft 31, to minimize the influence of the magnetic flux generated from the winding group 22 of the stator 20.

Note that Figure 1 shows a case where the main magnet section and the sensor magnet section are composed of a single magnet 40, but the main magnet section and the sensor magnet section may also be composed of separate magnets.

The magnetic sensor 50 may be configured using a Hall IC whose output signal is a digital signal, or a Hall element whose output signal is an analog signal. That is, the magnetic sensor 50 may be configured to detect the position of the rotor 30 using a Hall IC, or a Hall element.

Furthermore, the Hall IC may be a Hall IC (first type Hall IC) that detects the position of the rotor 30 using the first type described below, or a Hall IC (second type Hall IC) that detects the position of the rotor 30 using the second type described below.

In a first-type Hall IC, the sensor section and amplifier section are composed of separate semiconductor chips. In this first-type Hall IC, the sensor section is composed of a semiconductor other than silicon, and the amplifier section is composed of silicon. Hereinafter, first-type Hall ICs will be referred to as non-silicon Hall ICs. In a second-type Hall IC, the sensor section and amplifier section are composed of a single silicon semiconductor chip.

Non-silicon Hall ICs have two built-in chips, so the sensor is positioned so that its center is different from the center of the IC body. The sensor in a non-silicon Hall IC uses a non-silicon semiconductor such as indium antimonide (InSb). Compared to silicon semiconductors, this non-silicon semiconductor has advantages such as better sensitivity and less offset due to stress distortion.

Next, the circuit configuration of the built-in board 11 shown in Figure 1 will be explained. Figure 2 is a diagram showing the circuit configuration of the built-in board provided in the electric motor according to the first embodiment. Figure 2 shows the built-in board 11, the winding group 22, and the magnetic sensor 50.

The built-in board 11 is equipped with an overcurrent detection resistor 75 and a control unit 70.

The control unit 70 is connected to the host system, the gate drive circuit 82, ground 79A, and the magnetic sensor 50. The control unit 70 is also connected to a low-voltage power supply 78 via connection point 48. The control unit 70 is also connected to ground 79C via connection points 41, 42, and an overcurrent detection resistor 75.

The gate drive circuit 82 is connected to the low-voltage power supply 78 via connection point 48 and to the high-voltage power supply 77 via connection point 47. The low-voltage power supply 78 outputs a lower voltage than the high-voltage power supply 77. The high-voltage power supply 77 is a bus power supply.

The gate drive circuit 82 is also connected to the inverter 81. The gate drive circuit 82 is also connected to the protection circuit 83 and ground 79B via connection point 43.

Protection circuit 83 is connected to connection point 41 and connection point 43. That is, protection circuit 83 is connected to ground 79C via connection point 41, connection point 42, and overcurrent detection resistor 75. Protection circuit 83 is also connected to ground 79B via connection point 43.

The inverter 81 is connected to the winding group 22 of the stator 20 and supplies current to the winding group 22 of the stator 20. The inverter 81 is also connected to ground 79C via connection point 42 and overcurrent detection resistor 75. Grounds 79A to 79C are common grounds at the same potential.

The inverter 81 is equipped with six power transistors 81A to 81F. In the inverter 81, the six power transistors 81A to 81F are configured separately. In other words, the six power transistors 81A to 81F are each configured as separate components (chips).

The gate drive circuit 82 may be configured as a single IC, or as three separate three-phase ICs. The gate drive circuit 82 and control unit 70 may also be configured as a single IC. The control unit 70 may also be configured as a single dedicated IC (control IC), or as a microcomputer (hereinafter referred to as "mc").

Power transistors 81A to 81F are constructed using superjunction MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), planar MOSFETs, IGBTs (Insulated Gate Bipolar Transistors), etc. Because large currents flow through power transistors 81A to 81F, they generate a lot of heat and require heat dissipation.

In embodiment 1, a case will be described in which the magnetic sensor 50 detects the magnetic pole position of the rotor 30 corresponding to the magnetic flux position, and the built-in board 11 controls the electric motor 1 based on the magnetic pole position. The built-in board 11 may perform sensorless control of the electric motor 1 while estimating the magnetic pole position from the current flowing through the winding group 22 and the voltage applied to and generated by the winding group 22. The built-in board 11 may also use an operational amplifier or the like to amplify the current signal obtained by using a shunt resistor and a current sensor for current detection. The built-in board 11 may also use a comparator to generate a signal from this current signal to the control unit 70 for overcurrent protection.

In the built-in board 11, the voltage (e.g., 15 V) that drives the gates of the power transistors 81A-81F may differ from the microcomputer power supply voltage (e.g., 5 V) that drives the control unit 70, such as a microcomputer. In this case, the electric motor 1 uses a regulator to generate one power supply from another power supply supplied externally. For example, the built-in board 11 is supplied with a 15 V power supply from an external source, and the regulator generates a 5 V power supply and supplies it to the built-in board 11. This regulator may be built into the gate drive circuit 82.

The inverter 81 converts the input DC voltage into a three-phase AC voltage consisting of U-phase, V-phase, and W-phase, and supplies it to the winding group 22 of the stator 20. Power transistor 81A is the U-phase upper arm power transistor, power transistor 81B is the V-phase upper arm power transistor, and power transistor 81C is the W-phase upper arm power transistor. Power transistor 81D is the U-phase lower arm power transistor, power transistor 81E is the V-phase lower arm power transistor, and power transistor 81F is the W-phase lower arm power transistor.

That is, power transistor 81A is the power transistor of the upper arm of U-phase, power transistor 81B is the power transistor of the upper arm of V-phase, and power transistor 81C is the power transistor of the upper arm of W-phase. Also, power transistor 81D is the power transistor of the lower arm of U-phase, power transistor 81E is the power transistor of the lower arm of V-phase, and power transistor 81F is the power transistor of the lower arm of W-phase.

As such, inverter 81 has multiple power transistors in the upper arm and multiple power transistors in the lower arm. In embodiment 1, the power transistors that switch more frequently in the upper arm or lower arm are distributed and arranged on the top surface (first surface) of built-in substrate 11 and the bottom surface (second surface) opposite the first surface. Also, in embodiment 1, the power transistor that switches less frequently in the upper arm or lower arm is arranged on the top surface of built-in substrate 11.

The electric motor 1 has U-phase winding 22U, V-phase winding 22V, and W-phase winding 22W as windings included in winding group 22. U-phase winding 22U is connected to power transistors 81A and 81D. V-phase winding 22V is connected to power transistors 81B and 81E. W-phase winding 22W is connected to power transistors 81C and 81F.

The gate drive circuit 82 controls the on and off of the power transistors 81A to 81F according to the switching signal received from the control unit 70.

Three magnetic sensors 50 are arranged around the winding group 22. Each of the three magnetic sensors 50 outputs a magnetic pole position signal corresponding to the position of the rotor 30 to the control unit 70. The electric motor 1, which is a brushless DC motor, obtains rotational power by switching six (in the case of a three-phase motor) power transistors 81A-81F at appropriate times according to the magnetic pole position of the rotor 30. The switching signals in this case are generated by the control unit 70.

In addition, when at least one of the inverter 81 and the gate drive circuit 82 becomes too hot, the protection circuit 83 turns off all power transistors 81A to 81F of the inverter 81 to prevent element damage due to high temperatures.

Overcurrent detection resistor 75 is connected to the lower arm switches of power transistors 81D-81F. Protection circuit 83 monitors the voltage of overcurrent detection resistor 75, and when the voltage of overcurrent detection resistor 75 reaches or exceeds a specific value, it turns off power transistors 81A-81F to prevent overcurrent from flowing through winding group 22, thereby achieving overcurrent protection. The overcurrent detection unit may be built into control unit 70 or gate drive circuit 82.

A temperature-sensing element (not shown) may be provided on the built-in substrate 11, etc. In this case, when the control unit 70 receives a signal from the temperature-sensing element indicating an abnormal temperature, it forcibly turns off the power transistors 81A to 81F to achieve overheat protection.

The control unit 70 generates a switching signal that controls the on and off of the power transistors 81A to 81F at a specific frequency (carrier frequency) in accordance with a speed command signal received from a higher-level system.

The control unit 70 performs pulse width modulation (PWM) control on the power transistors 81A-81F by outputting a switching signal to the gate drive circuit 82. The control unit 70 estimates the magnetic pole position of the rotor 30 based on the magnetic pole position signal input from the magnetic sensor 50, and calculates the rotation speed of the rotor 30 from the estimated magnetic pole position. The control unit 70 outputs a rotation speed signal indicating the calculated rotation speed to a higher-level system.

The electric motor 1, which is a brushless DC motor, generates rotational power by switching six power transistors 81A to 81F (in the case of a three-phase motor) at appropriate timing depending on the magnetic pole position of the magnet 40 on the rotor 30. The switching signals used for this switching are generated by the control unit 70. The operating principle of this electric motor 1 will be explained below.

In the electric motor 1, the control unit 70 estimates the magnetic pole position of the rotor 30 based on the magnetic pole position signal from the magnetic sensor 50 or the current value of the current flowing through the winding group 22. The control unit 70 generates switching signals for switching the power transistors 81A-81F in accordance with the magnetic pole position of the rotor 30 and the speed command signal output from the higher-level system. The gate drive circuit 82 switches the power transistors 81A-81F on and off in accordance with the switching signals generated by the control unit 70.

The energization methods used by electric motor 1 include 120° energization control, 150° energization control, and sinusoidal energization control.

For example, with 120° conduction control, the on/off switching timing of the six power transistors 81A-81F is the same as the rising and falling edges of the detection signals from the three Hall ICs. Therefore, with 120° conduction control, the control unit 70 can be configured as a combinational circuit that does not require a clock.

On the other hand, for control that requires estimation of the magnetic pole position, such as 150° energization control, sinusoidal wave energization control, phase control, and sensorless control, the control unit 70 is composed of complex digital circuits including a clock. When estimating the magnetic pole position, for example, the timing between each rising and falling edge of the detection signals from three Hall ICs is precisely estimated.

Sensorless control is control that does not use a magnetic sensor 50. In sensorless control, the magnetic pole position is estimated from the current value detected by a current detection resistor, current detection transformer, etc., and control is performed. In sensorless control, signals detected by a current detection resistor, current detection transformer, etc. may be amplified using an operational amplifier, etc., as necessary.

As described above, the control unit 70 adjusts the voltage applied to the winding group 22 by PWM control of the power transistors 81A to 81F. The motor 1 may switch only one of the upper and lower arms to reduce losses due to switching of the inverter 81.

Now, we will explain the switching performed by the electric motor 1. Figure 3 is a diagram for explaining an example of switching performed by the electric motor according to the first embodiment. Figure 3 shows gate signals (switching signals) to power transistors 81A to 81F. The inverter 81 according to the first embodiment performs control in which the upper arm and the lower arm have different switching frequencies.

The gate signal to power transistor 81A, which is the U-phase upper arm power transistor, is U-phase upper gate signal 93A. The gate signal to power transistor 81B, which is the V-phase upper arm power transistor, is V-phase upper gate signal 93B. The gate signal to power transistor 81C, which is the W-phase upper arm power transistor, is W-phase upper gate signal 93C.

The gate signal to power transistor 81D, which is the U-phase lower arm power transistor, is U-phase lower gate signal 93D. The gate signal to power transistor 81E, which is the V-phase lower arm power transistor, is V-phase lower gate signal 93E. The gate signal to power transistor 81F, which is the W-phase lower arm power transistor, is W-phase lower gate signal 93F.

Figure 3 shows a timing chart of the gate signals of each power transistor 81A to 81F when the upper arm switches more frequently than the lower arm during a specific period T1 (in the case of upper arm switching).

When the gate signal is high, the power transistor is on, and when the gate signal is low, the power transistor is off. In the timing chart shown in Figure 3, the upper arm switches at a shorter cycle than the lower arm. The control unit 70 controls the motor 1 by changing the voltage applied to the winding group 22 by changing the switching duty of this upper arm.

The following describes the configuration of the electric motor 1 using an example in which the upper arm switches more frequently than the lower arm during a specific period T1 (upper arm switching). Note that the electric motor 1 of embodiment 1 can be applied to lower arm switching in the same way as it is to upper arm switching.

Figure 4 is a diagram showing the positioning of power transistors arranged on the built-in substrate of the electric motor according to embodiment 1. Figure 4 schematically shows the surface of the built-in substrate 11 on the side opposite the stator (the top surface, which is the surface that does not face the stator 20). Note that Figure 4 does not show the through-hole (the hole through which the rotating shaft 31 passes) formed in the built-in substrate 11.

With respect to the built-in substrate 11, one of the six power transistors 81A to 81F is arranged on the stator side (bottom surface) of the built-in substrate 11, and the remaining five are arranged on the opposite side (top surface) of the built-in substrate 11. Figure 4 shows the case where the upper arm power transistor 81B is arranged on the stator side of the built-in substrate 11, and the remaining power transistors 81A, 81C to 81F are arranged on the opposite side.

In this way, the power transistors of the arm with the greater number of switching times (power transistors that are more likely to heat up) are distributed across the stator-side and anti-stator-side surfaces of the built-in substrate 11. This allows the built-in substrate 11 to avoid heat concentration on the built-in substrate 11, making it possible to suppress temperature increases in the power transistors 81A to 81F. Therefore, the built-in substrate 11 can significantly suppress temperature increases in the built-in substrate 11.

When three upper arm power transistors are arranged in a specific direction on the built-in substrate 11, the central one of the three upper arm power transistors is arranged on the stator side, which greatly reduces heat concentration on the built-in substrate 11.

When viewed from above, the built-in substrate 11 has pairs of upper and lower arms for each phase arranged in the radial direction (direction from the center to the outer periphery). That is, when viewed from above, the built-in substrate 11 has pairs of upper and lower arms for the U phase arranged along the radial direction (first radial direction), pairs of upper and lower arms for the V phase arranged along the radial direction (second radial direction), and pairs of upper and lower arms for the W phase arranged along the radial direction (third radial direction).

When the built-in substrate 11 is viewed from above, three-phase upper arms are arranged side by side in the circumferential direction (first circumferential direction) relative to the axial direction of the rotating shaft 31, and three-phase lower arms are arranged side by side in the circumferential direction (second circumferential direction). As a result, the power transistors of the upper arms and the power transistors of the lower arms are arranged in two rows along the circumferential direction on the top surface of the built-in substrate 11. The circumferential directions (first circumferential direction and second circumferential direction) of the built-in substrate 11 are directions that follow the outer periphery of the built-in substrate 11.

Figure 4 shows the case where power transistors 81A to 81C are arranged along the circumferential direction when the built-in substrate 11 is viewed from above. Also, Figure 4 shows the case where power transistors 81D to 81F are arranged along the circumferential direction when the built-in substrate 11 is viewed from above.

In embodiment 1, for example, power transistors 81A and 81C are arranged on the top surface of the built-in substrate 11, and power transistor 81B is arranged on the bottom surface of the built-in substrate 11. Furthermore, power transistors 81D to 81F are arranged on the top surface of the built-in substrate 11.

This arrangement of power transistors 81A to 81F makes it easier to pattern wire the power transistors 81A to 81F. In this case, the power transistor of the upper arm with the higher switching frequency is arranged on the outer periphery, and the power transistor of the lower arm with the lower switching frequency is arranged on the inner periphery.

In other words, on the built-in substrate 11, the power transistors of the arm with a higher switching count are arranged closer to the outer periphery than the power transistors of the arm with a lower switching count. Furthermore, at least one of the power transistors with a higher switching count is arranged on the bottom surface of the built-in substrate 11.

In this way, the power transistor with the greater number of switching times (here, the upper arm power transistor) is arranged on the outer periphery, and one of the upper arm power transistors (here, power transistor 81B) is arranged on the stator side of the built-in substrate 11.

The power transistor 81B arranged on the stator side is susceptible to temperature rise due to the influence of the winding group 22, but because the power transistor 81B is arranged closer to the outer periphery than the lower arm power transistors, heat is more easily dissipated from the side of the electric motor 1. In this way, heat from the power transistor 81B arranged on the stator side is more easily dissipated from the side of the electric motor 1, improving the heat dissipation performance of the built-in board 11. In other words, by arranging the power transistor with a higher switching count closer to the outer periphery, heat generated by the power transistor with a higher switching count is more easily dissipated from the side of the electric motor 1, thereby significantly suppressing temperature rise.

When the arm with the greater number of switching times is the lower arm, the power transistors of the lower arm are arranged circumferentially on the outer side of the power transistors of the upper arm. At least one of power transistors 81D to 81F (for example, power transistor 81E) is arranged on the bottom surface of the built-in substrate 11.

Figure 5 is a cross-sectional view schematically showing a first example of the internal configuration of the electric motor according to the first embodiment. Note that power transistors 81D to 81F, which are lower arm power transistors, are not shown in Figure 5. While Figure 5 shows a case in which power transistor 81A and power transistor 81B are positioned opposite each other across built-in substrate 11, as shown in Figure 4, power transistor 81B may be positioned so as not to face power transistors 81A and 81C.

For example, of the power transistors 81A to 81C that are upper arm power transistors, power transistors 81A and 81C are arranged on the opposite side of the built-in substrate 11 from the winding group 22. In other words, power transistors 81A and 81C are arranged on the opposite side of the built-in substrate 11 from the stator. In other words, when the stator core 21 and winding group 22 are arranged opposite the bottom surface of the built-in substrate 11, power transistors 81A and 81C are arranged on the top surface, which is the surface opposite the bottom surface of the built-in substrate 11. This makes power transistors 81A and 81C less susceptible to the effects of heat emitted from the winding group 22. Therefore, the built-in substrate 11 can suppress temperature increases in power transistors 81A and 81C.

Furthermore, of the power transistors 81A to 81C, which are upper arm power transistors, power transistor 81B is arranged on the stator side of the built-in substrate 11. In other words, power transistor 81B is arranged on the bottom surface of the built-in substrate 11. This makes power transistor 81B less susceptible to the effects of heat emitted from power transistors 81A and 81C. Therefore, the built-in substrate 11 can suppress the temperature rise of power transistor 81B.

In addition, power transistor 81A may be arranged on the stator side of built-in substrate 11, and power transistors 81B and 81C may be arranged on the opposite side of built-in substrate 11 from the stator. Alternatively, power transistor 81C may be arranged on the stator side of built-in substrate 11, and power transistors 81A and 81B may be arranged on the opposite side of built-in substrate 11 from the stator.

Furthermore, two of the power transistors 81A to 81C may be arranged on the stator side of the built-in substrate 11.

Power transistors 81D to 81F are arranged on the opposite stator side of the built-in substrate 11. As such, the number of power transistors arranged on the opposite stator side is greater than the number of power transistors arranged on the stator side. Since the opposite stator side of the built-in substrate 11 has better heat dissipation properties than the stator side, arranging more power transistors on the opposite stator side improves heat dissipation.

Figure 6 is a cross-sectional view schematically showing a second example of the internal configuration of the electric motor according to the first embodiment. Note that power transistors 81D to 81F, which are lower arm power transistors, are not shown in Figure 6. While Figure 6 shows a case in which power transistor 81A and power transistor 81B are positioned opposite each other across built-in substrate 11, as shown in Figure 4, power transistor 81B may be positioned so as not to face power transistors 81A and 81C.

Figure 6 shows a case where the electric motor 1 is equipped with a heat sink 5. The heat sink 5 dissipates heat generated by the electric motor 1. The other configurations of the electric motor 1 equipped with the heat sink 5 are the same as those of the electric motor 1 shown in Figure 5. For example, in the electric motor 1, the heat sink 5 may be provided on the opposite stator side of the built-in substrate 11. In this case, the heat sink 5 is arranged on the opposite stator side of the built-in substrate 11 via the molded resin 12. The heat sink 5 is either integrally molded with the built-in substrate 11 using the molded resin 12, or attached after the molded resin 12 and the built-in substrate 11 are integrally molded. In this case, a heat dissipation member is arranged between the heat sink 5 and the molded resin 12 to reduce the contact thermal resistance between the heat sink 5 and the molded resin 12. Examples of heat dissipation members include a thermally conductive sheet, thermally conductive grease, or a thermal pad.

Although the axial heights of the heat dissipation patterns (heat dissipation substrate pattern 2A, described below) of the power transistors 81A, 81C arranged on the opposite side to the stator and the bodies or heat dissipation tabs of the power transistors 81A, 81C arranged on the opposite side to the stator are not uniform, the opposite side of the built-in substrate 11 is filled without gaps with molded resin 12. This allows the power transistors 81A, 81C on the opposite side to be joined to the heat sink 5 by the molded resin 12, which is filled without gaps. This prevents the thermal conduction of the heat sink 5 from being significantly reduced due to gaps, etc.

If the molded resin 12 is not integrally molded with the built-in substrate 11, a heat dissipation pad is placed between the heat sink 5 and the power transistors 81A, 81C or the heat dissipation pattern. In this case, if the height of the bodies of the power transistors 81A, 81C and the height of the heat dissipation pattern are not aligned, it becomes difficult to fill the heat dissipation pad without gaps between the heat sink 5 and the built-in substrate 11. On the other hand, in embodiment 1, the molded resin 12 is integrally molded with the built-in substrate 11, making it possible to fill the molded resin 12 without gaps between the heat sink 5 and the built-in substrate 11.

The heat dissipation tab (heat dissipation tab 85T described later) of the power transistor arranged on the stator side is also connected to the heat dissipation pattern (heat dissipation substrate pattern 2B described later). Then, molding resin 12 is arranged to cover the power transistor having the heat dissipation tab 85T.

In this way, in the electric motor 1, of the power transistors in the upper arm and the lower arm, at least one power transistor of the arm that switches more frequently is arranged on each side of the built-in substrate 11. In other words, in the electric motor 1, the power transistors of the arm that switches more frequently are distributed and arranged on the top and bottom surfaces of the built-in substrate 11.

In the electric motor 1, the arm with a higher switching count experiences a greater temperature rise than the arm with a lower switching count. For this reason, distributing the power transistors of the arm with a higher switching count to the top and bottom surfaces of the built-in substrate 11 greatly suppresses temperature rise.

In addition, through holes may be formed in the built-in substrate 11 to improve the heat dissipation of the power transistors arranged on the stator side. Here, we will explain the configuration of the built-in substrate 11 when through holes are formed.

Figure 7 is a diagram schematically illustrating a first example of the arrangement of power transistors on an embedded substrate according to embodiment 1. Figure 7 shows a cross-sectional view of an embedded substrate 11 when a through hole 4 is formed.

A heat dissipation board pattern 2A is arranged on the top surface (the surface opposite the stator) of the built-in board 11, and a heat dissipation board pattern 2B is arranged on the bottom surface (the surface facing the stator) of the built-in board 11. The heat dissipation board patterns 2A and 2B are patterns that diffuse heat generated by the built-in board 11. The heat dissipation board pattern 2A is the first heat dissipation board pattern, and the heat dissipation board pattern 2B is the second heat dissipation board pattern.

In addition, the power transistor 81B, which is arranged on the bottom side of the built-in substrate 11, has a heat dissipation tab 85T to improve heat dissipation. The heat dissipation tab 85T dissipates heat generated by the power transistor 81B.

The heat dissipation board pattern 2B is connected to the heat dissipation tab 85T. The heat dissipation board pattern 2B connected to the heat dissipation tab 85T is connected to the heat dissipation board pattern 2A on the opposite side to the stator via a through hole 4. The through hole 4 is a hole that penetrates the built-in board 11. A material having a thermal conductivity higher than a specific value may be embedded in the through hole 4. For example, a material having a thermal conductivity higher than that of the built-in board 11 may be embedded in the through hole 4.

With this configuration of the built-in substrate 11, the power transistor 81B dissipates heat through the heat dissipation tab 85T, the heat dissipation substrate pattern 2B, the through hole 4, and the heat dissipation substrate pattern 2A.

The power transistors 81A, 81C, 81D to 81F arranged on the upper surface of the built-in substrate 11 may have a heat dissipation tab 85T. The built-in substrate 11 may not have a heat dissipation tab 85T. In this case, the power transistor 81B is not connected to the heat dissipation tab 85T.

Figure 8 is a diagram schematically illustrating a second example of the arrangement of power transistors on an embedded substrate according to embodiment 1. Figure 8 shows a cross-sectional view of an embedded substrate 11 when a through hole 4 is formed.

Even if a heat dissipation tab 85T is not arranged on the built-in substrate 11, a heat dissipation substrate pattern 2A is arranged on the top surface (the surface opposite the stator) of the built-in substrate 11, and a heat dissipation substrate pattern 2B is arranged on the bottom surface (the surface facing the stator) of the built-in substrate 11.

When the heat dissipation tab 85T is not placed on the built-in substrate 11, the lower part of the package of the power transistor 81B, which becomes hot, is connected to the heat dissipation board pattern 2B. The heat dissipation board pattern 2B connected to the lower part of the package of the power transistor 81B is then connected to the heat dissipation board pattern 2A on the opposite side of the stator via the through hole 4. With this configuration, the power transistor 81B dissipates heat via the heat dissipation board pattern 2B, the through hole 4, and the heat dissipation board pattern 2A.

Here, we will explain the configuration of the electric motor of the comparative example. Figure 9 is a cross-sectional view that schematically shows the internal configuration of the electric motor of the comparative example. In the electric motor 1X of the comparative example, the power transistors 81A to 81F are all arranged on the same surface (top surface) of the built-in substrate 11X. In other words, in the electric motor 1X of the comparative example, the power transistors 81A to 81C are arranged on the surface of the built-in substrate 11X opposite the winding group 22. Note that the power transistors 81D to 81F are not shown in Figure 9.

In the electric motor 1 of embodiment 1, of the power transistors 81A to 81C, the power transistors 81A and 81C are arranged on the opposite side of the built-in substrate 11 from the winding group 22. Therefore, the built-in substrate 11 provided in the electric motor 1 of embodiment 1 can suppress temperature rise more than the built-in substrate 11X provided in the electric motor 1X of the comparative example. In other words, the built-in substrate 11 provided in the electric motor 1 of embodiment 1 is able to suppress temperature rise to a greater extent because components with a large amount of temperature rise are not arranged on only one side of the built-in substrate 11.

In this way, in the electric motor 1 of embodiment 1, the power transistors of the upper or lower arm that switches more frequently are distributed across the top and bottom surfaces of the built-in substrate 11. This allows the electric motor 1 to significantly suppress temperature increases in the built-in substrate 11, which serves as the control substrate.

Embodiment 2.
Next, a second embodiment will be described with reference to Fig. 10. In the second embodiment, the electric motor 1 described in the first embodiment is applied to an air conditioner.

Figure 10 is a schematic diagram of an air conditioner according to embodiment 2. The air conditioner 200 comprises an indoor unit 210 and an outdoor unit 220 connected to the indoor unit 210. The indoor unit 210 is equipped with an electric motor 1, an indoor unit board 211, and an indoor unit blower (not shown). The outdoor unit 220 is equipped with an outdoor unit blower 223.

The outdoor unit blower 223 and the indoor unit blower each incorporate the electric motor 1 described in embodiment 1 as their drive source. In particular, when the air conditioner 200 is for commercial use, high output and high heat dissipation performance are required, so applying the electric motor 1 described in embodiment 1 increases the heat dissipation effect.

In addition to the air conditioner 200, the electric motor 1 can also be mounted and used in other devices, such as ventilation fans, home appliances, and machine tools.

According to embodiment 2, the electric motor 1 described in embodiment 1 is applied to the air conditioner 200, thereby significantly suppressing the temperature rise of the built-in board 11.

The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or different embodiments may be combined with each other. Parts of the configuration may also be omitted or modified without departing from the spirit of the invention.

1, 1X Electric motor, 2A, 2B Heat dissipation board pattern, 4 Through hole, 5 Heat sink, 10 Molded stator, 11, 11X Built-in board, 12 Molded resin, 13 Lead wire, 14 Lead outlet, 20 Stator, 21 Stator core, 22 Winding group, 22U U-phase winding, 22V V-phase winding, 22W W-phase winding, 23 Insulator, 30 Rotor, 31 Rotating shaft, 32 Rotor insulation part, 33 Output side bearing, 34 Non-output side bearing, 40 Magnet, 41-43, 47, 48 Connection point, 50 Magnetic sensor, 60 Bracket, 61 Press-fit part, 70 Control part, 75 Overcurrent detection resistor, 77 High-voltage power supply, 78 Low-voltage power supply, 79A-79C Ground, 81 Inverter, 81A-81F Power transistor, 82 Gate drive circuit, 83 Protection circuit, 85T Heat dissipation tab, 93A U phase upper gate signal, 93B V phase upper gate signal, 93C W phase upper gate signal, 93D U phase lower gate signal, 93E V phase lower gate signal, 93F W phase lower gate signal, 200 Air conditioner, 210 Indoor unit, 211 Indoor unit board, 220 Outdoor unit, 223 Outdoor unit blower.

Claims (8)

A stator;
A rotor;
a control board having an inverter circuit for supplying current to the stator;
Equipped with
the inverter circuit has a plurality of upper arm power transistors and a plurality of lower arm power transistors,
power transistors of the upper arm or the lower arm, whichever arm switches more frequently, are distributed and arranged on a first surface and a second surface opposite to the first surface of the control board;
Electric motor. the second surface is a surface on which the stator is disposed, and the number of power transistors disposed on the first surface is greater than the number of power transistors disposed on the second surface;
2. The electric motor according to claim 1. The control board
the plurality of power transistors of the upper arm are arranged along a first circumferential direction when viewed from above the first surface of the control board, and the plurality of power transistors of the lower arm are arranged along a second circumferential direction when viewed from above the first surface of the control board, so that the plurality of power transistors of the upper arm and the plurality of power transistors of the lower arm are arranged in two rows along the circumferential direction when viewed from above the first surface of the control board,
the power transistor of the arm with a larger number of switching times is disposed on the first surface of the control board on an outer circumferential side of the power transistor of the arm with a smaller number of switching times,
2. The electric motor according to claim 1 . the power transistor disposed on the second surface has a heat dissipation tab for dissipating heat generated by the power transistor;
a first heat dissipation substrate pattern, which is a pattern for diffusing heat generated by the control substrate, is disposed on the first surface of the control substrate;
a second heat dissipation substrate pattern, which is a pattern for diffusing heat generated by the control substrate, is disposed on the second surface of the control substrate;
the heat dissipation tab is connected to a second heat dissipation board pattern, and the first heat dissipation board pattern and the second heat dissipation board pattern are connected via a through hole that penetrates the control board.
2. The electric motor according to claim 1 . a first heat dissipation substrate pattern, which is a pattern for diffusing heat generated by the control substrate, is disposed on the first surface of the control substrate;
a second heat dissipation substrate pattern, which is a pattern for diffusing heat generated by the control substrate, is disposed on the second surface of the control substrate;
the first heat dissipation substrate pattern and the second heat dissipation substrate pattern are connected via a through hole that penetrates the control board.
2. The electric motor according to claim 1 . Further comprising a heat sink for dissipating heat;
The control board is integrally molded using resin,
the heat sink is disposed on the first surface of the control board via the resin;
2. The electric motor according to claim 1 . An electric motor according to any one of claims 1 to 6,
Air conditioner. an inverter circuit for supplying a current to a stator of an electric motor having a stator and a rotor;
the inverter circuit has a plurality of upper arm power transistors and a plurality of lower arm power transistors,
power transistors of the upper arm or the lower arm, whichever arm switches more frequently, are distributed and arranged on a first surface and a second surface opposite to the first surface on a substrate;
Control board.